Patent application title: VIDEO DISPLAY DEVICE

Abstract:

Information about an emergency warning is received. When the emergency
warning condition is determined not to have occurred, the display power
mode is determined based on the selection of the viewer. When the
emergency warning condition is determined to have occurred, the display
power mode is automatically changed to the super-low power consumption
mode which reduces the power consumption, while the original video
information is displayed as it is by cutting down or changing part of the
video information. Thus, the screen display can be automatically reduced
to the minimum level that allows the viewer to obtain information,
thereby minimizing the power consumption of video display.

Claims:

1. A video display device comprising:a display power mode selection part
for outputting an indication signal corresponding to a display power mode
based on a selection action;an emergency warning determination part for
receiving information about an emergency warning, and determining that an
emergency warning condition has occurred, based on the information;a
display power mode determination part for receiving an output signal of
each of the display power mode selection part and the emergency warning
determination part;determining a display power mode based on an output of
the display power mode selection part when the emergency warning
condition is determined to have not occurred; and providing the display
control part instructions to switch the display power mode to a super-low
power consumption mode, regardless of the output of the display power
mode selection part when the emergency warning condition is determined to
have occurred;a display part for displaying video; anda display control
part for controlling the display part so that video information is
displayed in a display power mode based on an indication signal of the
display power mode determination part so as to be displayed as actual
video.

2. The video display device of claim 1, whereinthe emergency warning
determination part comprises:an additional information extraction part
for extracting additional information added to acquired video audio
information; andan emergency warning analysis part for determining
whether the emergency warning condition has occurred or not, based on the
information about the emergency warning contained in the additional
information.

3. The video display device of claim 2, whereinthe emergency warning
analysis part determines whether the emergency warning condition has
occurred or not by acquiring information about a flag and area code of an
emergency information descriptor contained in the additional information.

4. The video display device of claim 1, whereinthe emergency warning
determination part comprises:an emergency warning reception part for
receiving an emergency warning signal which is announced outside;
determining that an input of the emergency warning signal indicates that
the emergency warning condition has occurred; and notifying the display
power mode determination part that the emergency warning condition has
occurred.

5. The video display device of claim 1, whereinthe emergency warning
determination part comprises:an emergency power supply operation
detection part for determining that the emergency warning condition has
occurred when receiving a signal indicating that an emergency power
supply installed outside starts operation.

6. The video display device of claim 1, whereinthe emergency warning
determination part comprises:a power failure detection part for
monitoring power supply supplied to the video display device; outputting
a power failure detection signal when the power supply is stopped over a
predetermined period of time; and continuing to output the power failure
detection signal even after the power supply is recovered.

7. The video display device of claim 1, whereinthe super-low power
consumption mode achieves power consumption reduction by the display
control part changing the video information so as to be displayed in
monochrome, and then reversing a monochromatic color and black on display
in such a manner that, of the monochromatic color and black, the color
consuming less power accounts for at least half of a screen area.

8. The video display device of claim 1, whereinthe super-low power
consumption mode achieves power consumption reduction by the display
control part changing the video information so as to be displayed in
monochrome, and then making the video information displayed in only one
of output colors of the display part.

9. The video display device of claim 1, whereinthe super-low power
consumption mode achieves power consumption reduction by the display
control part changing the video information so as to be displayed in
monochrome, and then further changing the video information in such a
manner that an area with a luminance lower than a specified level is made
not to emit light, and an area with a luminance higher than the specified
level is displayed with the specified level of luminance.

10. The video display device of claim 1, whereinthe super-low power
consumption mode achieves power consumption reduction by the display
control part changing the video information in such a manner that an area
of a display range is reduced to not more than 1/2 by one of thinning out
and interpolation, and that an area other than the display range is made
not to emit light.

11. The video display device of claim 1 further comprising:a subtitle
extraction part for extracting subtitle information and forming the
subtitle information into information for screen display, whereinthe
super-low power consumption mode achieves power consumption reduction by
the display control part changing video on the display part in such a
manner that motion information is undisplayed; a background is blackened;
and the subtitle information is exclusively displayed in one of white and
a color other than black.

12. The video display device of claim 1, whereinthe display part is a
liquid crystal display device comprising a liquid crystal panel and
backlights; andthe super-low power consumption mode achieves power
consumption reduction by the display control part reducing a number of
the backlights to be turned on to not larger than 1/2 of a number in a
normal viewing condition.

13. The video display device of claim 1, whereinthe display part is a
liquid crystal display device comprising a liquid crystal panel, a
backlight, a light guide panel for guiding light of the backlight, and a
light-emitting part located on a side surface of the light guide panel;
andthe super-low power consumption mode achieves power consumption
reduction by the display control part turning on the backlight and
turning off the light-emitting part.

14. The video display device of any one of claims 1 to 6, whereinthe
display part is a liquid crystal display device comprising: a liquid
crystal panel; a backlight; and at least one of a light guide panel for
guiding light of the backlight and a diffused panel for diffusing light
transmitted by the light guide panel,the at least one of the light guide
panel and the diffused panel contains phosphorescent material diffused
therein, the phosphorescent material being excited by the light of the
backlight and emitting light even after extinction of excitation light,
andthe super-low power consumption mode achieves power consumption
reduction by the display control part turning off the backlight and
normally driving the liquid crystal panel.

Description:

[0002]In general, video display devices typified by television receivers
can provide large quantities of information in no time through the screen
display. The screen display, however, operates at high power, thus
causing television receivers to require higher power consumption than
radio receivers, which output audio only. Therefore, various video
display devices provided with the function of reducing power consumption
during viewing have been suggested.

[0003]One example of the conventional video display devices provided with
the function of reducing power consumption is disclosed in Japanese
Patent Unexamined Publication No. 2000-10068. The device suggested here
achieves power consumption reduction and at the same time provides
optimum display quality by making the video display luminance
automatically controlled based on the ambient brightness detected by a
means for detecting the amount of outdoor light.

[0004]Japanese Patent Unexamined Publication No. 2003-345297 discloses a
display device which achieves power consumption reduction by decreasing
the luminance of the original video without a sense of discomfort by
multiplying an input video signal by luminance-reducing characteristics.
The characteristics are characterized in that the luminance is gradually
reduced from the screen center to the screen edges, and in that the
screen edges have a region with a fixed luminance value.

[0005]Japanese Patent Unexamined Publication No. S56-24880 suggests a
control device which achieves power consumption reduction of a receiver
by changing the voltage of a deflection circuit so as to change the
screen size of a cathode ray tube display device.

[0006]Japanese Utility Model Unexamined Publication No. S62-30482 suggests
a display device which achieves power consumption reduction by
controlling chrominance signals so as not to display one or two colors
out of the three colors: red, blue and green.

[0007]Japanese Patent Unexamined Publication No. H11-196342 discloses a
conventional television receiver which can reduce standby power
consumption of a receiving terminal receiving digital television
broadcasts, and can receive an emergency warning broadcast even during
the standby period.

[0008]The last-mentioned conventional technique will be described as
follows with FIG. 16. FIG. 16 is a block diagram showing the structure of
the conventional video display device. In FIG. 16, program information
generation/delivery device 901, which is provided for digital television
broadcasting such as satellite broadcasting, includes seizure signal
delivery part 913 directly notifying the viewer about a program change or
an emergency broadcast by using a method other than a broadcast route
such as satellite waves. Receiving terminal 902 includes seizure signal
input part 924 for receiving the notice. The seizure signal activates
input part 921 via power control part 925. Input part 921 monitors
information being entered, and receives information about changes in
programs that are scheduled by the viewer to be videotaped or about an
emergency broadcast. If there is something to be updated in program
information stored in program information storage part 923, input part
921 updates it. When the acquisition and update of necessary information
are over, power supply to the input part is stopped. If there is
information about an emergency broadcast, power supply to the display
part is started so as to display the content of the emergency broadcast
on a display device. While reducing the power consumption of the terminal
in this manner, the terminal program is automatically updated in
accordance with the time changes of the programs that are scheduled to be
videotaped.

[0009]Video display devices such as television receivers, which provide
large quantities of information in no time through the screen display,
are powerful as a means for people to collect information in the event of
a disaster like an earthquake or typhoon. However, in the event of a
disaster, electricity and other supplies might be stopped. Under such a
situation, when there is an emergency power supply like a self-generating
system, people can use electric devices, but are required to use less
electricity than in the normal time. In disaster areas, on the other
hand, the power supply becomes unstable if not stopped completely, so
that people in the areas are forced to save electricity.

[0010]The aforementioned conventional technique, however, achieves power
consumption reduction substantially without degrading the image quality
of video display than the normal viewing condition. In other words, the
technique is intended to reduce power consumption, while maintaining the
visibility in the normal viewing condition high enough for the viewer to
enjoy programs. Thus it is impossible to expect a forcible and drastic
power reduction that is required in the event of an emergent disaster.
Therefore, when power is shut off in the event of an emergency or
disaster such as an earthquake, in houses and facilities having
self-generating systems like solar batteries, stored power is exhausted
too soon for the viewers to collect information.

[0011]Although the conventional video display device is useful in terms of
information collection because of its ability to receive an emergency
warning broadcast, the power saving technique can achieve a power
consumption reduction only in the standby state, and cannot be used to
save power for the viewer to collect information in the event of an
emergency or disaster.

SUMMARY OF THE INVENTION

[0012]In order to solve the aforementioned problem, the video display
device of the present invention includes: a display power mode selection
part for outputting an indication signal indicating a display power mode
based on the viewer's selection action; an emergency warning
determination part having a means for receiving information about an
emergency warning and determining that an emergency warning condition has
occurred, based on the information; a display power mode determination
part for receiving the output signal of each of the display power mode
selection part and the emergency warning determination part, and
determining the display power mode based on the output of the display
power mode selection part when the emergency warning condition is
determined to have not occurred, and providing the display control part
instructions to switch the display power mode to a super-low power
consumption mode which achieves power consumption reduction, regardless
of the output of the display power mode selection part when the emergency
warning condition is determined to have occurred, while the original
video information is displayed as it is by cutting down or changing part
of the video information; a display part for displaying video; and a
display control part for controlling the display part so that video
information is displayed in the display power mode based on the
indication signal of the display power determination part so as to be
displayed as actual video.

[0013]According to the video display device of the present invention thus
structured, when a disaster such as an earthquake takes place and an
emergency warning condition occurs in which power consumption reduction
is needed, the screen display is automatically reduced to the minimum
level that allows the viewer to obtain information, thereby minimizing
the power consumption of video display. Thus, the present invention
provides a video display device capable of securing information
collection for a long time in the event of an emergency or disaster.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a block diagram showing the structure of a video display
device according to a first embodiment of the present invention.

[0015]FIG. 2A shows an example of display in a super-low power consumption
mode according to the first embodiment of the present invention.

[0016]FIG. 2B shows an example of display in the super-low power
consumption mode according to the first embodiment of the present
invention.

[0017]FIG. 3A shows another example of display in the super-low power
consumption mode according to the first embodiment of the present
invention.

[0018]FIG. 3B shows another example of display in the super-low power
consumption mode according to the first embodiment of the present
invention.

[0019]FIG. 4A shows another example of display in the super-low power
consumption mode according to the first embodiment of the present
invention.

[0020]FIG. 4B shows another example of display in the super-low power
consumption mode according to the first embodiment of the present
invention.

[0021]FIG. 5 shows an example of the selection screen of the super-low
power consumption mode according to the first embodiment of the present
invention.

[0022]FIG. 6 is a block diagram showing the structure of a video display
device according to a second embodiment of the present invention.

[0023]FIG. 7A shows an example of display in a super-low power consumption
mode according to the second embodiment of the present invention.

[0024]FIG. 7B shows an example of display in the super-low power
consumption mode according to the second embodiment of the present
invention.

[0025]FIG. 8 is a block diagram showing the structure of a video display
device according to a third embodiment of the present invention.

[0026]FIG. 9 is a cross sectional view showing the structure of a display
part according to a fourth embodiment of the present invention.

[0027]FIG. 10 shows an example of control in a super-low power consumption
mode according to the fourth embodiment of the present invention.

[0028]FIG. 11 shows an example of control in the super-low power
consumption mode according to the fourth embodiment of the present
invention.

[0029]FIG. 12 shows an example of control in the super-low power
consumption mode according to the fourth embodiment of the present
invention.

[0030]FIG. 13 is a block diagram showing the structure of a video display
device according to a fifth embodiment of the present invention.

[0031]FIG. 14 is a block diagram showing the structure of a video display
device according to a sixth embodiment of the present invention.

[0032]FIG. 15 is a circuit diagram showing an example of the structure of
a power failure detection part according to the sixth embodiment of the
present invention.

[0033]FIG. 16 is a block diagram showing the structure of a video display
device according to the conventional technique.

[0065]A first embodiment of a video display device of the present
invention will be described as follows with drawings.

[0066]FIG. 1 is a block diagram showing the structure of the video display
device according to the first embodiment of the present invention. The
video display device of the present embodiment is intended to be a video
display device (a digital television receiver) for receiving digital
broadcasting. The video display device of the present invention can be a
device provided with a means for acquiring video information and a means
for displaying the video information. Specific examples are: television
receivers receiving digital or analog satellite or terrestrial
broadcasting; CATVs receiving cable broadcasting; and personal computers
capable of acquiring information through a network such as the Internet
and displaying the information on the screen.

[0067]In FIG. 1, television antenna 102 receives digital broadcasting.
Tuner/demodulation part 103 converts signals received by television
antenna 102 into a transport stream (hereinafter, "TS"). TS decoder 104
decodes the TS outputted from tuner/demodulation part 103 and outputs it
as a video and audio stream. MPEG decoder 105 MPEG-decodes the video
stream sent from TS decoder 104. Display control part 106 controls
display part 107 so as to display the video stream as actual video.

[0068]Additional information extraction part 109 extracts information
other than the video and audio stream from the TS, such as additional
information and control information. Emergency warning analysis part 110
determines whether an emergency warning for the occurrence of a disaster
has been announced or not from the extracted additional information. In
the present first embodiment, additional information extraction part 109
and emergency warning analysis part 110 make up emergency warning
determination part 115 which receives information about an emergency
warning and determines that an emergency warning condition has occurred,
based on the information. Display power mode selection part 112 outputs
an indication signal indicating the display power mode which is selected
by the viewer. Display power mode determination part 111 determines the
display power mode based on the respective output signals of emergency
warning analysis part 110 and of display power mode selection part 112,
and provides instructions to display control part 106.

[0069]Video display device 101 of the present first embodiment has three
display power modes as follows. A first mode is a normal power mode in
which a normal amount of power is consumed with the normal screen
display; a second mode is a power saving mode in which power consumption
is reduced by lowering the luminance than in the normal power mode,
without cutting down or changing the screen information; and a third mode
is a super-low power consumption mode in which power consumption is more
reduced than in the power saving mode by cutting down or changing part of
the video information, instead of displaying the original video
information as it is. It should be noted that the super-low power
consumption mode does not include the power consumption reduction
achieved by uniformly lowering the video display luminance.

[0070]Operation of video display device 101 of the present invention thus
structured will be described as follows.

[0071]In general, the viewer watches a program either in the normal power
mode or the power saving mode by setting it in display power mode
selection part 112. In this case, display control part 106 receives the
indication signal indicating the display power mode from display power
mode determination part 111 based on the selection result of display
power mode selection part 112. When the normal power mode has been
selected, display control part 106 makes display part 107 display video
without changing the data of the decoded video stream and at the normal
luminance level. On the other hand, when the power saving mode has been
selected, display control part 106 makes display part 107 display video
without changing the data of the decoded video stream, but at a lower
luminance level than the normal luminance level. In these modes, the
viewer can enjoy a program sent from a broadcast station in the original
condition, although different viewers have different preferences in
luminance level.

[0072]The operation of video display device 101 of the present invention
will be described on the assumption that a disaster has occurred and an
emergency warning has been announced from a broadcast station.

[0073]First of all, information to be multiplexed into an MPEG TS will be
described. The information to be multiplexed into the TS includes PSI
(Program Specific Information) as control information and SI (Service
Information) as interface information for the user to select programs, in
addition to the information to be provided to the viewer such as video
and audio data, subtitle information and data broadcasting. The
information contained in the PSI is organized in a variety of tables, and
one of the tables is a PMT (Program Map Table) which describes
information about the program components contained in the TS. The
information arbitrarily described here includes an emergency information
descriptor. The emergency information descriptor makes its flag "ON" in
the event of an earthquake or its warning announcement or when there is
an emergency warning broadcast such as a tidal wave warning, and
describes detailed information about the emergency warning such as area
code or warning level.

[0074]For example, assume that an earthquake has occurred and video
display device 101 has received a digital broadcasting wave in which the
flag of the emergency information descriptor is "ON". In FIG. 1,
television antenna 102 receives digital broadcasting, and
tuner/demodulation part 103 converts it into a TS. TS decoder 104 decodes
the TS outputted from tuner/demodulation part 103 and outputs it as a
video and audio stream.

[0075]Additional information extraction part 109 extracts information
other than the video and audio stream from the TS, such as additional
information and control information, and checks the emergency information
descriptor in the extracted PMT. When the flag of the emergency
information descriptor is "OFF", additional information extraction part
109 outputs a signal indicating that there is no emergency information.
On the other hand, when the flag of the emergency information descriptor
is "ON", additional information extraction part 109 continues to extract
the information about the area code and warning level, and outputs a
signal indicating that an emergency warning is currently broadcast, and
further outputs the extracted information about the area code and warning
level.

[0076]Emergency warning analysis part 110 receives the signal indicating
whether an emergency warning is currently broadcast or not, and further
receives the information about the area code and warning level from
additional information extraction part 109 when the emergency warning is
currently broadcast, thereby determining whether the emergency warming
condition has occurred or not. The term "emergency warning condition"
used in the present application indicates a condition in which there is a
possibility of a disaster, and power consumption should be restricted.

[0077]More specifically, when an emergency warning is not being broadcast,
emergency warning analysis part 110 determines that the emergency warning
condition has not occurred. If the emergency warning is being broadcast,
emergency warning analysis part 110 first checks the area code. Emergency
warning analysis part 110, which stores the area code of the area where
video display device 101 is located, compares it with the extracted area
code. When these area codes are different, emergency warning analysis
part 110 determines that the emergency warning condition has occurred in
another area and not in the area where video display device 101 is
located. When these area codes match each other, emergency warning
analysis part 110 determines whether the warning level exceeds a
specified level or not. When it exceeds the specified level, emergency
warning analysis part 110 determines that the emergency warning condition
has occurred, and when it does not exceed the specified level, emergency
warning analysis part 110 determines that the emergency warning condition
has not occurred.

[0078]Display power mode determination part 111 receives information
indicating whether the emergency warning condition has occurred or not
from emergency warning analysis part 110 and determines the display power
mode. When the emergency warning condition has not occurred, it obviously
means that the normal condition is present, so that display power mode
determination part 111 determines the display power mode based on the
output of display power mode selection part 112 as described above. On
the other hand, however, when the emergency warning condition has
occurred, display power mode determination part 111 switches the display
to the super-low power consumption mode, regardless of the output of
display power mode selection part 112.

[0079]Display control part 106 receives an indication signal indicating
the super-low power consumption mode from display power mode
determination part 111, and changes the data in the video stream to a
prescribed display content in the super-low power consumption mode or
provides specific setting controls to display part 107. As a result, of
all power consumption modes available, the lowest power consumption mode
is achieved that can display some form of information.

[0080]The following is a description about an example of display in the
super-low power consumption mode in the first embodiment.

[0081]When display part 107 is, for example, a plasma display device, the
display power changes in accordance with the area and intensity of the
luminescent cells in video display. It goes without saying that the power
consumption reduces as the display area or the number of the luminescent
cells gets smaller. Furthermore, the power consumption reduces with
decreasing luminescent intensity or average luminance.

[0082]FIGS. 2A and 2B show examples of display in the super-low power
consumption mode according to the first embodiment of the present
invention. First, video signal data to be displayed is converted to black
and white on display. The display area ratio between the white area and
the black area (the hatched area) is calculated, and when the white area
is larger, white and black are reversed to make the white area smaller on
display. This can drastically reduce power consumption as compared with
the normal viewing condition. Since the display video is displayed in
monochrome in this case, if the green luminescent cells, for example, are
exclusively made to emit light, the number of the luminescent cells used
for light emission is reduced to 1/3, thereby further drastically
reducing the power consumption.

[0083]In other examples shown in FIGS. 3A and 3B, the areas whose
luminance values are not higher than the specified luminance are made
black with the lowest luminance so as to eliminate the power consumption
in the areas. The other areas whose luminance values are higher than the
specified luminance are made gray (the shaded area) with the specified
luminance so as to further drastically reduce the power consumption.

[0084]In other examples shown in FIGS. 4A and 4B, the number of display
dots is reduced to 1/2 or 1/3 by thinning the dots out or by generating
complementary data. As a result, video display range 131a in FIG. 4A is
decreased to video display range 131b in FIG. 4B so as to reduce the
light-emitting area, thereby achieving a drastic power consumption
reduction.

[0085]These processes for cutting down or changing part of the video
information will damage the original video information, and therefore are
not suitable for the viewer to enjoy programs in the normal viewing
condition. Even so, however, these processes can help the viewer to
acquire a variety of information from the video information in the
emergency warning condition. Moreover, these processes have the effect of
drastically reducing power consumption, as compared with displaying the
original video information as it is.

[0086]It should be noted that the aforementioned processes to achieve the
super-low power consumption mode can be solely provided as functions of
the present invention, or two or more processes can be combined to
achieve the super-low power consumption mode. The latter case achieves a
further drastic power consumption reduction.

[0087]It is alternatively possible to provide a plurality of functions to
achieve a plurality of super-low power consumption modes so that the
viewer can choose one of them. In this case, as shown in FIG. 5, the
screen formed by actually changing a normal broadcast is displayed as a
selection screen, so that the viewer can see what the screen will look
like after the process of cutting down or changing part of the video
information, and can also see about what the power consumption will be as
compared with the normal condition. This can reflect the preferences of
the viewer and achieve super-low power consumption in the emergency
warning condition.

[0088]The super-low power consumption mode is cancelled when the viewer
selects a display power mode other than the super-low power consumption
mode via display power mode selection part 112. More specifically, when
the viewer selects either the normal power mode or the power saving mode
in display power mode selection part 112, the selected display power mode
is notified to display power mode determination part 111, which provides
display control part 106 with instructions to switch the selection mode.

[0089]However, display power mode determination part 111 can be made to
determine to continue video display in the super-low power consumption
mode without honoring the viewer's selection when the emergency warning
analysis part is continuously outputting the determination indicating the
presence of the emergency warning condition. It is alternatively possible
to add an indication item to cancel the super-low power consumption mode
as one more option in the display power mode. In this case, after the
canceling, the super-low power consumption mode is switched to the
display power mode that was previously selected.

[0090]As described hereinbefore, according the video display device of the
first embodiment of the present invention, when a disaster such as an
earthquake takes place and the emergency warning condition occurs in
which power consumption reduction is needed, the screen display is
automatically reduced to the minimum level that allows the viewer to
obtain information, thereby minimizing the power consumption of video
display.

Second Exemplary Embodiment

[0091]A second embodiment of the video display device of the present
invention will be described as follows with reference to drawings. The
same components as those in the first embodiment will be referred to with
the same reference remarks as those in the first embodiment, and their
description will be omitted as appropriate.

[0092]FIG. 6 is a block diagram showing the structure of a second
embodiment of video display device 201 of the present invention. FIG. 6
includes the same components as those in the first embodiment shown in
the block of FIG. 1: namely, television antenna 102; tuner/demodulation
part 103, TS decoder 104, MPEG decoder 105; display part 107; additional
information extraction part 109; emergency warning analysis part 110;
display power mode selection part 112; and display power mode
determination part 111. The description of these components will be
omitted.

[0093]FIG. 6 differs from FIG. 1 in providing subtitle extraction part 108
and display control part 206 which has a slightly different function from
display control part 106. Subtitle extraction part 108 extracts subtitle
information and character information in data broadcasting out of the
information multiplexed into the TS from the output of TS decoder 104,
and constitutes information for screen display. The character information
for the screen display is transmitted to display control part 206, and is
usually displayed on display part 107 as telop 132 or character
information on screen as shown in FIG. 7A.

[0094]In general, in the event of a disaster such as an earthquake, little
information is available immediately after the earthquake. As the initial
report, the occurrence, area and magnitude of the earthquake are
displayed as a telop (subtitle information). Thus, when a disaster
occurs, it is extremely useful for the viewer to have subtitle
information available as a means to collect information.

[0095]The following is a description of the operation of the video display
device of the present second embodiment. Note that the operation of
determining that the emergency warning condition has occurred out of the
additional information contained in the TS, and of changing the display
screen of display part 107 to the super-low power consumption mode by
display control part 206 at the instruction of display power mode
determination part 111 in the case of the emergency warning condition
will be omitted because it is equal to that in the first embodiment
described with FIG. 1.

[0096]When the emergency warning condition has occurred, in order to
display the character information transmitted from subtitle extraction
part 108 as a telop, display control part 206 displays the data after
changing it as follows.

[0097]FIG. 7B shows an example of display in the super-low power
consumption mode according to the present second embodiment. Display
control part 206 first discriminates telop 132 from an input signal, and
then changes the video on display part 107 in such a manner that motion
information is undisplayed; the background is blackened (the hatched
area); and telop 132 is exclusively displayed either in white or a color
other than black. As a result, as shown in FIG. 7B, a telop (subtitle
information) about emergency information is exclusively displayed on the
screen having no light emission.

[0098]This allows display information to be displayed after being
drastically reduced in size so as to make sure to display the information
desired by the viewer in the emergency warning condition, while
drastically reducing power consumption as compared with the normal
viewing condition.

[0099]It is alternatively possible that the aforementioned operation is
performed only when the descriptor in the PMT indicates that the
emergency warning broadcast includes subtitle information only, and when
the entire video stream broadcast content is determined to be the
emergency warning broadcast, the screen with a subtitle composed on
screen is displayed in another super-low power consumption mode shown in
the first embodiment. This makes sure to display the information desired
by the viewer, while drastically reducing power consumption depending on
the type of the information.

[0100]There are cases where subtitle information about an emergency
warning is transmitted after being composed in video. In these cases, the
subtitle information can be extracted from the video, and as shown in
FIG. 7B, the video information can be displayed after being processed in
such a manner that the video areas other than the subtitle are blackened
with no light emission.

[0101]According to the video display device of the second embodiment of
the present invention, when a disaster such as an earthquake takes place
and the emergency warning condition occurs in which power consumption
reduction is needed, the screen display is automatically reduced to the
minimum level that allows the viewer to obtain information, thereby
minimizing the power consumption of video display.

Third Exemplary Embodiment

[0102]The first and second embodiments have shown the cases where the
occurrence of the emergency warning condition in the event of a disaster
such as an earthquake is determined based on the emergency warning
descriptor multiplexed into a broadcast wave. Besides these cases, there
are other cases where an emergency warning is announced independently.
The announcement can be done by wireless or cable connected to the
individual houses in the area.

[0103]A third embodiment of the present invention, on the other hand,
provides the video display device of the present invention with an
emergency warning reception part as a means for detecting the occurrence
of a disaster. The same components as those in the aforementioned
embodiments will be referred to with the same reference remarks as those
in the embodiments, and their description will be omitted as appropriate.

[0104]FIG. 8 is a block diagram showing the structure of the video display
device according to the present third embodiment. FIG. 8 differs from
FIG. 6 in providing emergency warning reception part 113 which receives
an emergency warning signal and notifies display power mode determination
part 311 that the emergency warning condition has occurred. FIG. 8
further differs from FIG. 6 in that display power mode determination part
311 takes the output of emergency warning reception part 113 into
consideration to determine the display power mode. In the present third
embodiment, either additional information extraction part 109 and
emergency warning analysis part 110 or emergency warning reception part
113, or both of them make up of emergency warning determination part 315,
which receives information about the emergency warning and determines
that the emergency warning condition has occurred based on the
information.

[0105]Video display device 301 is structured to receive an emergency
warning signal from outside. The emergency warning signal is received by
a dedicated receiver when transmitted by wireless, and the output is
connected with video display device 301. On the other hand, when the
emergency warning signal is transmitted by cable to individual houses,
the signal line is connected with video display device 301 either
directly or after being branched.

[0106]The operation of video display device 301 thus structured will be
described as follows. The operation for emergency warning analysis part
110 to determine whether or not the emergency warning condition has
occurred out of the additional information in the TS extracted by
additional information extraction part 109, and then to notify the result
to display power mode determination part 311 will be omitted because it
is equal to the operation in the second embodiment.

[0107]When an emergency warning is announced independently without being
multiplexed into a broadcast wave, the emergency warning signal is
entered to emergency warning reception part 113. Emergency warning
reception part 113 determines that the emergency warning condition has
occurred from the input of the emergency warning signal, and notifies it
to display power mode determination part 311. Display power mode
determination part 311 receives the information about whether or not the
emergency warning condition has occurred from emergency warning analysis
part 110 and emergency warning reception part 113 so as to determine the
display power mode. When the outputs of these blocks do not indicate the
occurrence of the emergency warning condition, display power mode
determination part 311 regards the condition as normal and determines the
display power mode based on the output of display power mode selection
part 112. On the other hand, however, when at least one of emergency
warning analysis part 110 and emergency warning reception part 113
notifies the occurrence of an emergency warning condition, display power
mode determination part 311 switches the display power mode to the
super-low power consumption mode, regardless of the output of display
power mode selection part 112.

[0108]Display control part 206 receives an indication signal indicating
the super-low power consumption mode from display power mode
determination part 311, and changes the data in the video stream to a
prescribed display content in the super-low power consumption mode or
provides setting controls to specific display part 107. As a result, of
all power consumption modes available, the lowest power consumption mode
is achieved that can display some form of information. The subsequent
display in the super-low power consumption mode is identical to that
described in the other embodiments, so that the description will be
omitted.

[0109]As described hereinbefore, according to the video display device of
the third embodiment of the present invention, when a disaster such as an
earthquake takes place and the emergency warning condition occurs in
which power consumption reduction is needed, the screen display is
automatically reduced to the minimum level that allows the viewer to
obtain information, thereby minimizing the power consumption of video
display.

[0110]The present third embodiment has described the case where whether or
not the emergency warning condition has occurred is determined by both
emergency warning analysis part 110 and emergency warning reception part
113. It is alternatively possible, however, to provide emergency warning
reception part 113 only so as to receive the emergency warning signal,
thus achieving the super-low power consumption mode.

[0111]The video display device of the present invention has been described
as a television receiver that receives digital broadcasting waves.
Alternatively, however, the video display device can be a television
receiver that receives analog broadcasting waves as long as it can
achieve the super-low power consumption mode by receiving an emergency
warning signal.

[0112]It is also possible to implement a standby state in which power is
supplied exclusively to the parts related to a means for extracting the
emergency warning descriptor from the additional information of the TS
and determining whether or not the emergency warning condition has
occurred, and to a means for receiving the emergency warning signal. In
this case, even if the viewer is not watching on the video display device
of the present invention, whether the emergency warning condition has
occurred or not can be determined in the standby state. When the viewer
starts to watch in this condition, the video is displayed in the
super-low power consumption mode from the beginning of viewing. As a
result, it is prevented to consume large power for display in the
emergency warning condition caused by a disaster or other reasons.

Fourth Exemplary Embodiment

[0113]A fourth embodiment will describe another example of display control
in the super-low power consumption mode when the display part is a liquid
display device. The block diagram showing the structure is identical to
FIG. 1, 6 or 8, and the operation including the determination of the
occurrence of the emergency warning condition is identical to that of the
first, second or third embodiment.

[0114]In general, in a liquid crystal display device, the luminance and
hue of the display video are not determined only by the signal to drive
the liquid crystal panel but are also determined by the backlights.
Consequently, the video information to be displayed is determined also by
the backlights and the light guide panel. The display power consumption
of the liquid crystal display device is hardly affected by the display
data, and is mainly made up of the power consumed by the backlights.
Therefore, in the power saving mode which reduces power consumption by
lowering the luminance, the power consumption reduction is achieved by
decreasing the luminance of the backlights. In this case, although the
whole luminance is lowered, the video information is maintained, thus
allowing the viewer to enjoy programs as usual.

[0115]The example of display control in the super-low power consumption
mode of the video display device of the fourth embodiment of the present
invention will be described as follows. First, the structure will be
described.

[0116]In FIG. 9, the video display device of the fourth embodiment of the
present invention is provided with a plurality of backlights 143 inside
case 148. The light of the backlights passes through light guide panel
144 and uniformly irradiates liquid crystal panel 147 from its back via
diffused panel 146. Besides backlights 143, the video display device is
also provided with miniature backlight 145. Thus, the display part of the
fourth embodiment is made up of backlights 143, light guide panel 144,
diffused panel 146, liquid crystal panel 147 and miniature backlight 145.

[0117]In the display part thus structured, in the super power consumption
mode, as shown in FIG. 10, backlights 143 that are shown as white circles
are exclusively turned on, and backlights 143 that are shown as black
circles (the hatched area) are turned off. Uniform image quality suitable
for the normal viewing is designed to be obtained by turning all
backlights 143 on. Therefore, with only some of backlights 143 turned on,
the video information is displayed nonuniformly by being affected by the
positions of the backlights that are turned on. Of course, this makes the
image quality too low for the viewer to enjoy the normal viewing. Even
so, however, reducing by half or more the number of backlights 143 to be
turned on which are provided on the back surface of the display device
reduces the power required to light backlights 143, thereby achieving a
drastic power consumption reduction as compared with the normal viewing
condition.

[0118]FIG. 11 shows another example in the super-low power consumption
mode according to the fourth embodiment of the present invention. In FIG.
11, besides backlights 143 which are normally used, the video display
device is also provided with miniature backlight 145 somewhere around
light guide panel 144. All of backlights 143 are turned off and miniature
backlight 145 is exclusively turned on in the super-low power consumption
mode, thereby further reducing the power consumption in the super-low
power consumption mode.

[0119]In a case where the super power consumption mode is achieved by
controlling the lighting of the backlights, and emergency information is
displayed by subtitle information, the backlights corresponding to the
positions to display the subtitle information can be turned on
exclusively with the other backlights turned off. In this case, the
necessary subtitle information can be displayed more clearly, while
drastically reducing the display power.

[0120]A drastic power consumption reduction can be also achieved without
lowering the visibility of the subtitle display so much by locating
miniature backlight 145 in accordance with the position of the subtitle
display as follows. For example, the subtitle information is determined
to be displayed on either the top or bottom of the screen, and when it is
displayed on the top, miniature backlight 145 is located on the top of
light guide panel 144, whereas when it is displayed on the bottom,
miniature backlight 145 is located on the bottom of light guide panel
144.

[0121]FIG. 12 shows further another example in the super-low power
consumption mode according to the fourth embodiment of the present
invention. In the structure shown in FIG. 12, one or both of light guide
panel 144 and diffused panel 146 contains phosphorescent material 157
diffused therein. As phosphorescent material 157, a material that can
emit phosphorescence long after the extinction of excitation light can be
selected.

[0122]The following is a description of the operation of the display part
thus structured. In the normal viewing condition with all of backlights
143 turned on, phosphorescent material 157 is excited by the light of the
backlights. Then, when the emergency warning condition occurs and the
super-low power consumption mode sets in, display control part 106 turns
off all of backlights 143, but normally drives liquid crystal panel 147.
As a result, phosphorescent material 157 contained in light guide panel
144 or diffused panel 146 can autofluoresce to provide video display for
a certain period in spite of all of backlights 143 being turned off.

[0123]This allows the viewer to obtain information as video in the
emergency warning condition such as a disaster, while achieving a drastic
reducing power consumption reduction, although the viewer cannot enjoy
programs with the normal image quality.

Fifth Exemplary Embodiment

[0124]A fifth embodiment will describe an example of the structure having
another means of determining the occurrence of the emergency warning
condition. The same components as those in the first to fourth
embodiments will be referred to with the same reference remarks as those
in the first to fourth embodiments, and their description will be omitted
as appropriate.

[0125]FIG. 13 is a block diagram showing the structure of an example of
the fifth embodiment of the present invention. In the situation where
video display device 501 of the present invention is installed, emergency
power supply 161 is also provided to operate when a disaster or the like
causes the power failure of the commercial power supply. Emergency power
supply 161 can be a power storage type, driven by a fuel cell or a solar
cell, or can be a generator driven by gasoline or the like.

[0126]Emergency power supply 161 is provided with power failure detection
part 162 which monitors the supply of commercial power supply 164. Power
failure detection part 162 makes emergency power supply 161 operate when
commercial power supply 164 stops the supply over the predetermined time
period, thus supplying the output of emergency power supply 161 in place
of commercial power supply 164. Emergency power supply operation
notification part 163, when emergency power supply 161 starts operation,
outputs a signal indicating this.

[0127]Emergency power supply operation detection part 166 provided in
video display device 501 of the present invention determines that the
emergency warning condition has occurred when notified by the output of
emergency power supply operation notification part 163 that emergency
power supply 161 has started operation. The situation in which a power
failure occurs and the emergency power supply starts operation indicates
a condition in which at least some form of accident, more likely a
disaster, has occurred and power consumption reduction is desperately
needed. Consequently, the information indicating that the emergency power
supply has started operation can be regarded as the information about the
emergency warning. Thus in the fifth embodiment, emergency power supply
operation detection part 166 makes up emergency warning determination
part 515 which receives information about an emergency warning and
determines that the emergency warning condition has occurred, based on
the information.

[0128]The subsequent operation in the case where the emergency warning
condition is determined to have occurred is identical to that in the
first to fourth embodiments, and display power mode determination part
111 acquires information indicating whether or not the emergency warning
condition has occurred from emergency power supply operation detection
part 166, and determines the display power mode. Since the emergency
warning condition has occurred in this case, the display power mode is
switched to the super-low power consumption mode regardless of the output
of display power mode selection part 112.

[0129]Display control part 106 receives an indication signal indicating
the super-low power consumption mode from display power mode
determination part 311, and changes the data in the video stream to a
prescribed display content in the super-low power consumption mode or
provides setting controls to specific display part 107. As a result, of
all power consumption modes available, the lowest power consumption mode
is achieved that can display some form of information.

[0130]As described above, according to the video display device of the
fifth embodiment of the present invention, when a disaster such as an
earthquake takes place and the emergency warning condition occurs in
which power consumption reduction is needed, the screen display is
automatically reduced to the minimum level that allows the viewer to
obtain information, thereby minimizing the power consumption of video
display. Thus, a video display device is provided which can secure
information collection for a long time in the event of an emergency or
disaster.

[0131]Since the video processing and display control in the super-low
power consumption mode are identical to those in the first to fourth
embodiments, their description will be omitted.

Sixth Exemplary Embodiment

[0132]Unlike the structure shown in the fifth embodiment, the power
failure detection part can be located inside the video display device. A
sixth embodiment will describe an example having such a structure.

[0133]In FIG. 14, power failure detection part 165 monitors the power
supply supplied to video display device 601, and when the power supply is
stopped over a predetermined period of time, outputs a power failure
detection signal and continues to output the signal even after the
recovery of the power supply. In order to invert the power failure
detection signal, a release pulse is outputted from display power mode
selection part 612.

[0134]FIG. 15 is a circuit diagram showing an example of the structure of
power failure detection part 165 according to the sixth embodiment of the
present invention. As shown in FIG. 15, power failure detection part 165
can be achieved by bistable multivibrator 171 provided with CR
integration circuit 176. CR integration circuit 176 which stores electric
charges supplied from the power supply is connected with low-output-side
input 173 of bistable multivibrator 171. When there is a power failure,
the electric charges of CR integration circuit 176 are discharged. Even
if the power supply is resumed, it takes time to recover the voltage of
CR integration circuit 176 so that output 174 of bistable multivibrator
171 is fixed to a low value. The output can be inverted by providing a
pulse to high-output-side input 172.

[0135]The following is a description of the operation of video display
device 601 of the sixth embodiment of the present invention thus
structured.

[0136]There are cases where power supply is once stopped in the event of a
disaster or the like, but is recovered by emergency power restoration. In
such a case, the temporary interruption of the supply from commercial
power supply 164 makes power failure detection part 165 invert a power
failure detection signal and output it to display power mode
determination part 311. Display power mode determination part 311
operates the power failure detection signal as a signal indicating the
emergency warning condition. The situation in which a power failure
occurs is considered to be a condition in which at least some form of
accident, more likely a disaster, has occurred and power consumption
reduction is desperately needed. Consequently, the information indicating
that a power failure has occurred can be regarded as the information
about the emergency warning. Thus in the sixth embodiment, power failure
detection part 165 makes up emergency warning determination part 615
which receives information about an emergency warning and determines that
the emergency warning condition has occurred, based on the information.

[0137]The subsequent operation in the case where the emergency warning
condition is determined to have occurred is identical to the operation in
the first to fifth embodiments, and the display power mode is switched to
the super-low power consumption mode regardless of the output of display
power mode selection part 612. As a result, the data in the video stream
is changed to a prescribed display content in the super-low power
consumption mode, or setting controls are provided to specific display
part 107, so that of all power consumption modes available, the lowest
power consumption mode is achieved that can display some form of
information. Since the video processing and display control in the
super-low power consumption mode are identical to those in the first to
fifth embodiments, their description will be omitted.

[0138]When determining that the emergency warning condition is gone, the
viewer can either select another display power mode in display power mode
selection part 612 or release the super-low power consumption mode. As a
result, display power mode selection part 612 outputs a release pulse to
invert the power failure detection signal, thereby releasing the
super-low power consumption mode.

[0139]As described hereinbefore, according to the video display device of
the sixth embodiment of the present invention, when a disaster such as an
earthquake takes place and the emergency warning condition occurs in
which power consumption reduction is needed, the screen display is
automatically reduced to the minimum level that allows the viewer to
obtain information, thereby minimizing the power consumption of video
display. Thus, a video display device is provided which can secure
information collection for a long time in the event of an emergency or
disaster.

INDUSTRIAL APPLICABILITY

[0140]The video display device of the present invention can automatically
reduce power consumption in the emergency warning condition such as a
disaster, and is useful as a video display device which acquires and
displays video information, such as television receivers, CATVs and
personal computers that acquire information through a network like the
Internet and display the information on the screen.